The Darren Lehmann case has exposed a double standard in the Australian cricket community. Normally, moments of the highest pressure in sport are held to reveal character. Steve Waugh's toughness and Shane Warne's genius are revealed precisely in the heat of the moment. Conversely, the touring Englishmen have been stripped naked - weak, timid, lacking in technique - under high heat. We beat the drum of our own supremacy because we're tough when it really matters.

Yet for Lehmann, the logic has been reversed. His defenders cannot reconcile his outburst against his Sri Lankan opponents with his reputation as a "good bloke". Team-mates and associates have described Lehmann's slur as an "out of character" act, committed "in the heat of the moment" by someone who is "universally regarded as a nice guy". Instead it is the Sri Lankans who are rendered villains, oversensitive and unmanly to complain.

How is it that for Lehmann the rule is waived? How is it that in the heat of the moment, he did something supposedly out of character?

The answer, of course, is that he did not. To believe this was the first time Lehmann used this terrible language about black people is to show the indulgence of a parent who believes their teenager's "it was my first joint" defence.

Lehmann's misfortune is that he is the man who got caught revealing the unwitting racism that infuses not only Australian cricketing culture but mainstream Australia.

Lehmann's supporters cannot understand the difference between calling someone a "cunt" and a "black cunt". Nor, presumably, can they understand that it is offensive for our media commentators to speak of the Sri Lankans as "babbling" in the field, as "leaping about with great big smiles" or as "little guys". Monkeys babble. Little black sambos have great big smiles.

We're not yet at a stage of cultural maturity where we even know what racism is. Our prime minister John Howard is supposedly a decent man who hates the racist epithet. Yet each year he sanctifies the white man's military tragedy (Gallipoli) while denying or excusing the black man's military tragedy (the colonisation massacres).

Racism in Australia is insidious, unadmitted. We have few proud racists. There is no open Klan or National Front here. Our white supremacist fringe - the 10% of voters represented in the late 1990s by Pauline Hanson but who, in the 2001 election, swung back into step with Howard's dance of Arab-phobia - do not admit to racism.

Hanson's platform of cutting non-white immigration and government assistance to Aborigines was coded as a call for "fairness" (no pun intended) from "mainstream Australia". When Howard talks of pre-emptive strikes against terrorists in Asia, and of de-democratising the rights of non-white asylum seekers, his favourite phrasing is "ordinary Australians think...". All ills can be cured if everybody just stops whingeing and swallows the (white, male, resolutely middle-class and anti-intellectual) panacea of 'mateship'.

By raising this, one risks being labelled politically-correct and a troublemaker. Three years ago, when India toured Australia, I interviewed Indian-Australians who were supporting India. I found two reasons.

One was that it is natural not to let go of one's birthplace. Presumably those Australians who impose cultural-assimilation policies upon new arrivals are not the ones who slag Greg Norman for his American accent; presumably those who say Muslims should renounce their language and religion once they become Australians are not the ones who accuse Clive James and Germaine Greer of "selling out" their Australian-ness to Britain.

Yet a more pungent reason for those Indian flags at the Sydney Cricket Ground was that fathers resented the exclusion of their sons from local and school teams. Every family I interviewed had a story of a boy who had been shut out of the "in" group because of his race, or his teetotalism, or some other cultural difference.

Lest this be taken as paranoia, one need only look at the make-up of Australian cricket teams at senior levels. The most common name in the Sydney phone book is Lee - and they're not relatives of Brett - yet all our teams can boast is the occasional Kasprowicz or Di Venuto. If you want a cultural snapshot of Australia in the 1950s, look no further than our cricket.

Rather than shame, our cricket community tends to feel pride in this ethnic wholeness. Yet the Lehmann case has shown that an excess of our greatest strengths - unity, certainty, simplicity - has become our greatest weakness.

Australian triumphalism masks the fact that we lag a generation behind England in resolving the race debate. While English sporting clubs struggle to harmonise different cultures, Australian clubs fix the problem by leaving non-whites out.

When controversy about England's racially diverse cricket teams has broken out, Australian cricketers tacitly agree with those who say recent teams from the old country are "less English", and therefore weaker, than in the 1960s or before. Their prescription for England's ills is to revert to "English" (i.e. Boycottian, Illingworthian) traits. We fail to recognise England's change as much as we fail to acknowledge our own.

When I wrote about the Indians who felt shut out of Australian cricket, I was taken to task for "inventing" trouble where none existed. Yet I'd seen racism with my own eyes. On a tour to India, I heard two Australian cricketers call the locals "niggers". I saw Australian cricketers coming across Indians sleeping on a railway platform in Jamshedpur and nudging them awake with their feet in order to take a happy snap.

No malice was intended, and if you can understand that the cricketers involved were both "good blokes" and yet-to-be-reconstructed racists, then you go a long way to comprehending the incoherence amid which most Australians live.

· Malcolm Knox is a former chief cricket correspondent for the Sydney Morning Herald and is the author of the novel Summerland, published in the UK by Picador.